1. Field of Invention
The invention relates to a screen, an optical component used in the screen, and a manufacturing method of the optical component and, in particular, to a rear projection screen, an optical component used in the rear projection screen, and a method for manufacturing the optical component.
2. Related Art
As the acceptance of HDTVs and DVD players has grown widespread, the image quality of large size displays has become increasingly important. Recently, rear projection screens are well developed. In a rear projection screen, images are projected on a screen and then are outputted to an audience. Therefore, it is very important to consider the view angles, the contrast and resolution of the images, and the brightness when designing the rear projection screen.
With reference to FIG. 1, a conventional rear projection screen 1 includes a Fresnel lens 10 and a lenticular lens 11. In this case, the lenticular lens 11 has a light entrance surface 110 and a light exit surface 111. The light entrance surface 110 has a plurality of cylindrical convex portions 110a. The light exit surface 11 is a planar surface. In order to increase the contrast and resolution of rear projection screen 1, the lenticular lens 11 might be tinted to absorb interference and scattered light in the environment.
In addition, the lenticular lens 11 may be mixed with light diffusing beads 120 to increase the view angle of the rear projection screen 1. However, while the lenticular lens 11 is tinted, the brightness and chromatic aberration may worsen.
To solve the above mentioned problems, referring to FIGS. 2A, 2B and 2C, U.S. Pat. No. 5,870,224 disclosed a rear projection screen 2 having a Fresnel lens 20 and a lenticular lens 21. The lenticular lens 21 has a light entrance surface 210, and a plurality of cylindrical convex portions 210a are formed on the light entrance surface 210. The lenticular lens 21 further has a light exit surface 211, which is a planar surface. Moreover, a transparent film 220 is provided on the light exit surface 211, and a plurality of light absorbing layers 230 are formed on the transparent film 220. In addition, a light diffusing layer 240 is formed on the light absorbing layers 230. As mentioned above, the interference and scattered light can be absorbed, and the view angle of the rear projection screen 2 can be increased. However, when an incident light 2000 passes through the light entrance surface 210, focuses on the light exit surface 211, and is scattered out of the lenticular lens 21, the light absorbing layers 230 may block the scattered light 2001. Thus, the brightness of the rear projection screen 2 is induced. Accordingly, the width and height of light absorbing layers 230 are limited. It should be noted that when the thickness of the lenticular lens 21 is produced incorrectly during the manufacturing process, the incident light 2000 might not focus on the light exit surface 211 accurately. Then, the brightness of rear projection screen 2 is further induced, and the width of light absorbing layers 230 must be further contracted to overcome this problem.
In addition, as shown in FIG. 2C, since the width of light absorbing layer 230 is limited, the interference light 2002 may penetrate through part of the light exit surface 211 without light absorbing layers 230 from environment, and turn into the reflecting light 2003 from the lenticular lens 21 through part of the light exit surface 211 without light absorbing layers 230. Therefore, the contrast and resolution of the rear projection screen 2 may be reduced.
U.S. Pat. No. 5,870,224 also disclosed a method for manufacturing a lenticular lens. In this case, an ultraviolet-sensitive resin film is coated on the transparent support film. Then, several light beams illuminate the lenticular lens. The lenticular lens focuses the light beams away from some regions and towards other regions of the ultraviolet-sensitive resin film. The regions onto which ultraviolet light beams are focused become the non-adhesive portions; the regions on which the ultraviolet light beams are focused away are the adhesive portions. According to this method, the light beams must be in parallel before passing through the light entrance surface, or a light mask is required to control the pitches of non-adhesive portions and adhesive portions. Accordingly, the fabricating of the lenticular lens becomes difficult and complex.
Hence, it is an important subject of the invention to absorb the interference and scattered light for increasing the brightness of the rear projection screen, to enlarge the area of light absorbing material for improving contrast and resolution of a rear projection screen, and to simplify the manufacturing processes of a lenticular lens.